2006-03-07 Joel Sherrill <joel@OARcorp.com>

	PR 866/rtems
	* score/include/rtems/system.h, score/include/rtems/score/isr.h,
	score/inline/rtems/score/thread.inl,
	score/macros/rtems/score/thread.inl: Added memory barriers to enter
	and exit of dispatching and interrupt critical sections so GCC will
	not optimize and reorder code out of a critical section.

5 files changed, 49 insertions, 8 deletions

diff --git a/cpukit/ChangeLog b/cpukit/ChangeLog
index 6b871c3776..66337501f9 100644
--- a/cpukit/ChangeLog
+++ b/cpukit/ChangeLog
@@ -1,3 +1,12 @@
+2006-03-07	Joel Sherrill <joel@OARcorp.com>
+
+	PR 866/rtems
+	* score/include/rtems/system.h, score/include/rtems/score/isr.h,
+	score/inline/rtems/score/thread.inl,
+	score/macros/rtems/score/thread.inl: Added memory barriers to enter
+	and exit of dispatching and interrupt critical sections so GCC will
+	not optimize and reorder code out of a critical section.
+
 2006-02-08	Thomas Rauscher  <trauscher@loytec.com>
 
 	PR 890/networking
diff --git a/cpukit/score/include/rtems/score/isr.h b/cpukit/score/include/rtems/score/isr.h
index 320332dfd7..1359e91fd8 100644
--- a/cpukit/score/include/rtems/score/isr.h
+++ b/cpukit/score/include/rtems/score/isr.h
@@ -104,7 +104,10 @@ void _ISR_Handler_initialization ( void );
  *  the argument _level will contain the previous interrupt mask level.
  */
 #define _ISR_Disable( _level ) \
-        _CPU_ISR_Disable( _level )
+  do { \
+    _CPU_ISR_Disable( _level ); \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+  } while (0)
 
 /**
  *  This routine enables interrupts to the previous interrupt mask
@@ -112,7 +115,10 @@ void _ISR_Handler_initialization ( void );
  *  enable interrupts so they can be processed again.
  */
 #define _ISR_Enable( _level ) \
-        _CPU_ISR_Enable( _level )
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    _CPU_ISR_Enable( _level ); \
+  } while (0)
 
 /**
  *  This routine temporarily enables interrupts to the previous
@@ -127,7 +133,11 @@ void _ISR_Handler_initialization ( void );
  *  properly protects itself.
  */
 #define _ISR_Flash( _level ) \
-        _CPU_ISR_Flash( _level )
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    _CPU_ISR_Flash( _level ); \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+  } while (0)
 
 /**
  *  This routine installs new_handler as the interrupt service routine
diff --git a/cpukit/score/include/rtems/system.h b/cpukit/score/include/rtems/system.h
index 59d5b293af..9558155daf 100644
--- a/cpukit/score/include/rtems/system.h
+++ b/cpukit/score/include/rtems/system.h
@@ -135,6 +135,17 @@ extern "C" {
 # define RTEMS_INLINE_ROUTINE
 #endif
 
+/**
+ *  The following macro is a compiler specific way to ensure that memory
+ *  writes are not reordered around certian points.  This specifically can
+ *  impact interrupt disable and thread dispatching critical sections.
+ */
+#ifdef __GNUC__
+  #define RTEMS_COMPILER_MEMORY_BARRIER() asm volatile("" ::: "memory")
+#else
+  #define RTEMS_COMPILER_MEMORY_BARRIER()
+#endif
+
 #ifdef RTEMS_POSIX_API
 /** The following is used by the POSIX implementation to catch bad paths.  */
 int POSIX_MP_NOT_IMPLEMENTED( void );
diff --git a/cpukit/score/inline/rtems/score/thread.inl b/cpukit/score/inline/rtems/score/thread.inl
index 1599883d70..125f7cf5f7 100644
--- a/cpukit/score/inline/rtems/score/thread.inl
+++ b/cpukit/score/inline/rtems/score/thread.inl
@@ -142,6 +142,7 @@ RTEMS_INLINE_ROUTINE void _Thread_Deallocate_fp( void )
 RTEMS_INLINE_ROUTINE void _Thread_Disable_dispatch( void )
 {
   _Thread_Dispatch_disable_level += 1;
+  RTEMS_COMPILER_MEMORY_BARRIER();
 }
 
 /**
@@ -154,6 +155,7 @@ RTEMS_INLINE_ROUTINE void _Thread_Disable_dispatch( void )
 #if ( CPU_INLINE_ENABLE_DISPATCH == TRUE )
 RTEMS_INLINE_ROUTINE void _Thread_Enable_dispatch()
 {
+  RTEMS_COMPILER_MEMORY_BARRIER();
   if ( (--_Thread_Dispatch_disable_level) == 0 )
     _Thread_Dispatch();
 }
@@ -171,6 +173,7 @@ void _Thread_Enable_dispatch( void );
 
 RTEMS_INLINE_ROUTINE void _Thread_Unnest_dispatch( void )
 {
+  RTEMS_COMPILER_MEMORY_BARRIER();
   _Thread_Dispatch_disable_level -= 1;
 }
 
diff --git a/cpukit/score/macros/rtems/score/thread.inl b/cpukit/score/macros/rtems/score/thread.inl
index b5b94799c8..3ace7af4e2 100644
--- a/cpukit/score/macros/rtems/score/thread.inl
+++ b/cpukit/score/macros/rtems/score/thread.inl
@@ -126,7 +126,10 @@
  */
 
 #define _Thread_Disable_dispatch() \
-  _Thread_Dispatch_disable_level += 1
+  do { \
+    _Thread_Dispatch_disable_level += 1; \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+  } while (0)
 
 /*PAGE
  *
@@ -136,9 +139,11 @@
 
 #if ( CPU_INLINE_ENABLE_DISPATCH == TRUE )
 #define _Thread_Enable_dispatch()  \
-      { if ( (--_Thread_Dispatch_disable_level) == 0 ) \
-             _Thread_Dispatch();  \
-      }
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    if ( (--_Thread_Dispatch_disable_level) == 0 ) \
+       _Thread_Dispatch(); \
+  } while (0)
 #endif
 
 #if ( CPU_INLINE_ENABLE_DISPATCH == FALSE )
@@ -152,7 +157,10 @@ void _Thread_Enable_dispatch( void );
  */
 
 #define _Thread_Unnest_dispatch()  \
-  _Thread_Dispatch_disable_level -= 1
+  do { \
+    RTEMS_COMPILER_MEMORY_BARRIER(); \
+    _Thread_Dispatch_disable_level -= 1; \
+  } while (0)
 
 /*PAGE
  *